If you are using free mendix cloud, one easy way to find is:
- In Sprintr, Click Show debugger Information button from environments which shows you the debugger link in URL. It will be like https://<random text>.mxapps.io/debugger. Remove the debugger in the last part and rest of it is your URL.
If your using paid Mendix cloud, you can find it by:
- navigating to environments section you will see the URL of appropriate Environments
If this does not answer your question, then explain your question in more detail.